It is well known to use electronic fuel injectors to supply the fuel demands of an automotive engine. Typical automotive engines use one of two types of injectors, commonly referred to as "saturation" and "peak and hold" injectors. The performance of these fuel injectors is generally sufficient for an automotive, four-stroke engine or for crankcase scavenged two-stroke engines where both the air and fuel delivered to the engine are passed through the crankcase. With those types of engines, the duration of the injection event is longer than that of a directly injected two-stroke engine.
In a directly injected two-stroke engine, the fuel injector is typically placed in communication with the combustion chamber through either a cylinder wall or the cylinder head. Thus, fuel is supplied directly from the fuel injector to the combustion chamber which greatly limits the time available to complete the injection event. The injection event is further limited in a two-stroke engine as compared to a four-stroke engine because of the high revolutions per minute (RPM) at which a two-stroke engine may operate, with a typical maximum RPM of a two-stroke engine at about 12,000 RPM'S. Still further, in a two-stroke engine the injection event occurs with every revolution of the crankshaft as compared to every other revolution in a four-stroke engine. These limitations provide a total available injection time of about 3 milliseconds or less at high engine speeds. The current electrical circuits used to drive the fuel injectors have a relatively long start delay which is the time required to open the fuel injector after the electrical signal has been sent to the injector to open it. With the limited available injection time, it is desirable if not necessary to minimize the start delay time to insure that adequate fuel can be delivered to the engine at high engine speeds and loads wherein the engine demands a high quantity of fuel. While peak and hold type injectors have reduced the start delay time as compared to saturation injectors, a relatively long start delay time remains and the high voltage power supply required by some peak and hold circuitry is expensive.